RESUMO
A general and efficient synthesis of CF3-containing 1,3-dioxolanes using Et3N-catalyzed ketalization/oxa-Michael cascade of quinols with trifluoromethyl ketones is described. The reaction works efficiently under mild reaction conditions and produces the desired products in 68%-95% yields with acceptable diastereoselectivities. In addition, the reaction proceeds smoothly to give the desired product 3a in 92% yield and with high ee (80%) in the presence of a chiral catalyst (DHQ)2PHAL.
RESUMO
A general and efficient synthesis of trifluoromethyl substituted 5-alkylidene-1,3-dioxolane using a silver salt and DBU cooperatively catalyzed nucleophilic addition/cyclization of propargylic alcohols and trifluoromethyl ketones is described. The procedure produced 5-alkylidene-1,3-dioxolane derivatives with good to excellent yields and can be used with a broad range of substrates.
RESUMO
The palladium-catalyzed enantioselective intramolecular C-H arylation of N-(2-haloaryl)-P,P-diphenylphosphinic amides furnishes P-stereogenic phosphine oxide derivatives in 61-99% yield with 88-97% ee. The catalyst generated in situ from a TADDOL-derived phosphoramide ligand and Pd(dba)2 is optimum in terms of yield and enantioselectivities.
RESUMO
The palladium-catalyzed intramolecular C-H arylation reaction of N-(2-bromoaryl)ferrocenecarboxamides furnishes planar chiral ferrocene derivatives. TADDOL-derived phosphoramide ligands induce enantioselectivities ranging from 91:9 to 98:2 er.
RESUMO
A facile and practical approach to preparation of enantiopure N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol was developed from cheap and easily available l-(+)-methionine. Synthetic highlights include the three-step, one-pot construction of the chiral azetidine ring and the development of an improved one-step procedure for the synthesis of the key intermediate l-2-amino-4-bromobutanoic acid. Enantiopure N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol was evaluated for catalytic asymmetric addition of organozinc reagents to aldehydes. The asymmetric ethylation, methylation, arylation, and alkynylation of aldehydes achieved enantioselectivity of up to 98.4%, 94.1%, 99.0%, and 84.6% ee, respectively, in the presence of a catalytic amount of chiral N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol. Our results demonstrated further that the four-membered heterocycle-based backbone was a good potential chiral unit for the catalytic asymmetric induction reaction, and the hindrance of the bulky ferrocenyl group, compared to a phenyl group, played an important role in the enantioselectivities. A possible transition for the catalytic asymmetric addition has been proposed on the basis of the crystal structure of the chiral ligand 3b including two HOAc molecules and previous studies.
Assuntos
Benzaldeídos/química , Compostos Ferrosos/química , Compostos Organometálicos/química , Álcoois/síntese química , Álcoois/química , Catálise , Compostos Ferrosos/síntese química , Ligantes , Conformação Molecular , Compostos Organometálicos/síntese química , EstereoisomerismoRESUMO
The asymmetric unit of the title compound, C(28)H(20)N(2)O(2)·0.5C(2)H(5)OH, contains two independent mol-ecules of 1,1'-[o-phenyl-enebis(nitrilo-methyl-idyne)]di-2-naphthol, denoted A and B, and one ethanol solvent mol-ecule. The hydr-oxy groups are involved in intra-molecular O-Hâ¯N hydrogen bonds influencing the mol-ecular conformations, which are slightly different in mol-ecules A and B, where the two bicyclic systems form dihedral angles of 51.93â (9) and 58.52â (9)°, respectively. In the crystal structure, a number of short inter-molecular Câ¯C contacts with distances of less than 3.5â Å suggest the existence of π-π inter-actions, which contribute to the stability of the crystal packing.
RESUMO
In the crystal structure of the title compound, {[Fe(2)(C(7)H(3)NO(4))(2)(H(2)O)(6)]·4H(2)O}(n), there are two types of coordination for the Fe(II) atoms. One Fe(II) atom is in a distorted octa-hedral N(2)O(4) environment, with two chelating rings from the pyridine-dicarboxyl-ate ligands and two O atoms from the water mol-ecules, while the other is in a distorted octa-hedral O(6) environment with two O atoms from the pyridine-dicarboxyl-ate ligands and four O atoms from the water mol-ecules. Both Fe(II) atoms lie on crystallographic centers of symmetry. The complex possesses an infinite chain structure running along the [101] direction. These chains are inter-connected by the uncoordinated water mol-ecules through O-Hâ¯O hydrogen bonds.